Manufacturers of systems employing circuits which transmit electrical power, including modern vehicle propulsion systems, are generally aware that it is not desirable for a service technician or other individuals to have physical contact with components or systems that are at elevated voltage levels. Typical high-voltage power systems employ energy storage devices requiring a certain amount of time to discharge stored electrical power prior to access. Examples of such energy storage devices include batteries, inductors, and capacitors. The potential energy of any such device must be discharged or dissipated before contact may safely occur. The process of discharging electrical energy takes a finite amount of time. To prevent premature physical contact, such systems often employ barriers to access, such as protective covers, and lock-out devices, which are elements of an interlock system.
An example of an interlock system is a high-voltage interlock system (‘HVIL’). A typical HVIL system employs one or more devices to open an electrical circuit to prevent current flow, or delay timers to permit discharge of a storage capacitor before access is permitted. An exemplary HVIL circuit includes a current-sensing device, referred to as an HVIL control circuit, placed electrically in series with a network of electrical switches. Each switch is attached to accessible components in a network supplied by a common power source. The HVIL control circuit functions as a monitoring system to assure electrical current (or voltage) in the HVIL loop stays within predetermined limits, and as an actuation device that can initiate all actions and processes necessary to discharge electrical power from all devices in the network. A schematic of an exemplary HVIL system is shown with reference to FIG. 1.
Presently available electrical switch devices for use in limiting access to a device in a HVIL system are costly, bulky devices that may permit premature access to an electrical system. Such switch devices may be difficult to reinstall into a system after service. Therefore, what is needed is a small, low-cost, low-mass device for use with an HVIL system to prevent premature or inadvertent contact with elevated voltage levels in an electrical system, especially one on a vehicle.